PHYLOGENETIC-RELATIONSHIPS OF NONAXENIC FILAMENTOUS CYANOBACTERIAL STRAINS BASED ON 16S RIBOSOMAL-RNA SEQUENCE-ANALYSIS

In order to determine the nearly complete 16S rRNA gene sequences of c yanobacteria originating from nonaxenic cultures, a cyanobacterium-spe cific oligonucleotide probe was developed to distinguish polymerase ch ain reaction (PCR) products of the cyanobacterial rRNA operons from th ose resulting from amplification of contaminating bacteria. Using this screening method the 16S rRNA genes of four nonaxenic filamentous cya nobacterial strains belonging to the genera Leptolyngbya and Oscillato ria were cloned and sequenced. For the genus Leptolyngbya, the 16S rRN A sequence of the axenic strain PCC 73110 was also determined. Phyloge netic trees were constructed based on complete and partial sequences. The results show that the strains Leptolyngbya foveolarum Komarek 1964 /112, Leptolyngbya sp. VRUC 135 Albertano 1985/1, and Leptolyngbya bor yanum PCC 73110 belong to the same cluster. Strain Oscillatoria cf. co rallinae SAG 8.92, which contains the rare photosynthetic pigment CU-p hycoerythrin, is not closely related to other CU-phycoerythrin-contain ing cyanobacteria. Oscillatoria agardhii CYA 18, which is a representa tive of planktonic Oscillatoria species that form toxic blooms in Norw egian inland waters, has no close relatives in the tree.